Emergency differential pressure gas supplying apparatus



March 22, 1960 R. D. cUMMlNs EMERGENCY DIFFERENTIAL PRESSURE GAS SUPPLYING APPARATUS Filed NOV. 6, 1956 2 Sheets-Sheet l INVENTOR. @JQ/mfc@ C March 22, 1960 R. D. CUMMINS 2,929,377

EMERGENCY DIFFERENTIAL PRESSURE GAS SUPPLYING APPARATUS Filed NOV. 6, 1956 2 Sheets-Sheet 2 93 V8 /HQQAE Q92 5f R f l; 25

United States., Per@ O ENUERGENCY DIFFERENTIAL PRESSURE GAS SUPPLYING APPARATUS Richard D. Cummins, Tonawanda, N.Y., assignor to Firewel Development Company, Bulfalo, N.Y., a co-partnership composed of Clifford Meidenhauer, Lancaster, N.Y., and Donald S. Nesbitt, Orchard Park, N.Y.

Application November 6, 1956, Serial No. 620,733

Claims. (Cl. 12S-144) 3.4 p.s.i.a. (pounds per square inch absolute)represents a critical value below which the aviator cannot go without pressure protection for his body since below about this 3.4 p.s.i.a., a persons blood will boil at normal temperatures. 3.4 p.s.i.a. corresponds to an altitude of about 35,000 feet. This protection can be provided by a pressurized cockpit for the airplane but it is apparent that if the cockpit pressure should fail because of failure of the cockpit pressurizing system or through a shell hole through the cockpit canopy, pressure protection must be provided by means of a pressure suit. .j

Further, by way of anticipating such emergency or failure` of the cockpit pressure, oxygen for preoxygenation must be supplied to the mask of the aviator at a pressure slightly higher than cockpit pressure. This oxygen is required because in the event of sudden decompression, as through failure of cockpit pressure, the aviator needs preoxygenation. Without suchpreoxygenation, at the time of sudden decompression thenitrogen in the aviators blood would in short time block oli certain of his blood vessels and cause aeroembolism because of the expansion of nitrogen in the blood due to reduc tion in pressure. To this same end the oxygen must be supplied at slightly greater than cockpit pressure to avoid leakage of cockpit air into the mask breathing system. Even relatively small amounts of nitrogen in the blood stream of the aviator at the time of sudden decompression could have extremely harmful results, and since cockpit air predominates in nitrogen rather than oxygen it is important that such leakage be prevented.

The suit protection, in the practice of the present ini vention, is provided by a so-called partial pressure or Henry suit. Such a partial pressure suit is in the form of a restraining garment having an inatable belly bladder over the aviators torso area in which the pressure can be the same as in the mask from which the aviator withdraws oxygen for respiration, i.e., 3.4 p.s.i.a. minimum. The remainder of the suit, particularly around the arms and legs, includes cords which alternately loop around the body and inatable tubes known in the art as capstans. Increasing the gas pressure within the tubes or capstans draws the body loops more tightly about the body of the aviator so as to increase the restraining pressure.

No restraining pressure is required until an altitude is reached which corresponds to about 3.4 p.s.i.a. atmospheric pressure or 35,000 feet. Above this altitude a suit pressure in the tubes is required which corresponds to a diterential between the 3.4 p.s.i.a. minimum pressure and the ambient pressure. Thus, the suit pressure should be the minimum pressure of 3.4 p.s.i.a. plus at 2,929,377 .Petafed Ms 2.2.1269.

least four times the diderential between this 3.4 p.s.i.a. and; any lower ambient pressure, the apparatus hereinafter described being calculated to provide a suit pressure, at lower than 3.4 p.s.i.a. ambient pressure, equal to 3.4 p.s.i.a. and from five to six times the differential between this pressure of 3.4 p.s.i.a. and vthe lower ambient pressure.

It is also desirable to provide apparatus which, in addition to providing suit pressure at sucha differential between such constant minimum pressure and ambient pressure, also supplies gas at such constant minimum pressure to the belly bladder protecting the respiratory organs of the aviator and also to supply such gas in the form of oxygen at such constant-minimum pressure for inhalation by the user. A

Also, while no harm results from applying suit pres` sure before mask and belly bladder pressure, harmcan result from applying mask and belly bladder pressures before suit pressure. Accordingly, where both mask' pressure and suit pressure is applied by the apparatus, it is important to provide apparatus insuring that thereis,y no mask or belly bladder pressure without suit pressure.`

It is also important, and the present invention particulv larly relates to this feature, that in the event of sudden depressurization of the cockpit, as through failure of the pressurization system or a shell hole through the canopy, that the mask oxygen pressure, suit bladder pressure, and pressure in the suit capstans or restraining tubes be im# mediately built up to the required respective values so as to enable the aviator to survive and complete his mission even when the failure of cockpit pressure occurs at alti,-- tudes higher than 35,000 feet. A

The invention also contemplates supplying oxygen under emergency suit, belly bladder, and mask pressures following bailout of the aviator so that he is ableto fall or parachute to altitudes lower than the critical 35,000 feet. Other objects and advantages of the present invention will be apparent from the following description and drawings in which: 'v1

Fig. l is a diagrammatic representation of a partial pressure suit and face mask and having the mask, belly bladder and suit capstans or restraining tubes pressurized by the apparatus forming the subject of the present in vention and which will function upon failure of cockpit pressure from any cause to build up and maintain the suit pressure, belly bladder pressure, and oxygen face mask pressure to the value required by the ambient pressure following failure of the articial cockpit pressure. Fig. 2 is a sectional view of the aneroid forming of the apparatus shown in Fig. 1.

Fig. 3 is a sectional view through the diaphragm valve mechanism which supplies oxygen to the mask and belly bladder and also through the diaphragm valve mechanism which serves to maintain the required suit pressure.

Fig. 4 is a sectional View, partly in elevation, of the par? mask injector which serves -to render the diaphragm valve mechanism for the mask oxygen partially self-energizing'. A similar injector is provided for rendering the diaphragm valve mechanism which supplies suit pressure partially self-energizing. l Fig. 5 is a section through a bypass valve controlling the effect of the mask injector in rendering the diaphragm valve mechanism partially self-energizing. Fig. 6 is a section through the relief valve which serves to unload all above 3.4 p.s.i.a. pressure from the mask when required because of cockpit decompression.

Fig. 7 is a section through the relief valve which serves to unload suit pressure when required on descent. In Fig. 1 of the drawings the pertinent parts of the` partial pressure suit, or Henry suit, so far as the present invention is concerned,I are represented by a face masls 3 1Q through which oxygen of the required pressure is supplied to the aviator for inhalation, a belly bladder 11 which in the suit is over the aviators torso area, and the pressure capstan or tube system 12. As previously indicated, the suit pressure capstans or tubes, indicated at 12, extend along the suit, particularly the arms and legs, and include cords (not shown) which alternately loopr around the body and the inflatable capstans or tubes 12 so that upon inliating the capstans or tubes 12 the body loops are drawn more tightly about the body of the aviator so as to increase the restraining pressure.

The oxygen for theY apparatus is supplied under relatively medium pressure, say 70 p.s.i.g. (pounds per square inch gage), through a supply line 15 containing a lilter The oxygen under such pressure can, under control of a valve 18, be supplied from the ships supply of oxygen through a supply line 19 or from an emergency bottle supply of oxygen through a supply line 20. Failure ofthe artificial pressurization of the cockpit, as by failure of the pressurizing system or a shell hole through the cockpit canopy, is not related to the ships supply of oxygen supplied through the line 19 and hence the ships supply of oxygen may be available to enable: the pilot to com plete his mission even following loss of cockpit pressure. In the event of bailout, the supply of medium pressure oxygen for operating the system would be from the line 20 This medium pressure ofthe oxygen, assumed to be 70 p.s.i.g., is maintained in a branch line 21 up to a constant size restricted orifice 22 which permits an oxygen ow of, say, 20 cubic centimeters per minute at the assumed 70 pounds pressure. Another lter 1'7 is shown as contained in this branch line 21 to protect the restricted orifice 22 and the apparatus therebeyond. This branch line 21 supplies oxygen to a constant pressure regulator 23, which can be set to maintain constant control pressure of, say, 3.4 .p.s.i.a. and is preferably constructed as follows:

The numeral 24 represents a hollow casing forming a chamber 25 and the bottom of which chamber is enclosed, by the bottom wall 26 of the casing which is preferably in the form of a screw plug. A bracket 2S of any suitable form is fixed within the casing, the bracket being shown in Fig. 2 as being of inverted cup-shaped form andl having an opening 29 so that the interior of the bracket issubject to the same pressure as that which obtains within the rest of the chamber 25. The purpose ofthe bracket is to support a sealed bellows member or aneroid 30. This aneroid has a corrugated tubular wall 31 enclosed by end heads 32 and 33, the end head 32 beingv fastened to the bracket 28 while the opposite end head 33 forms a valve head arranged to seat against the end of a tubular adjusting vent stem 35. This tubular adjusting vent stem is in the form of` a screw having an through bore or vent 36 and screwed into a threaded hole 38 in the bottom wall or screw plug 26 and which hole alines with the axis of expansion of the aneroid 30. The vent 36 is open to the atmosphere within the cockpit, the pressure of which is hereinafter referred to as ambient pressure, the apparatus being designed to operate when any artificial or pressurized atmosphere in the cockpit is lost as through flame-out of the engine.

' Referring to Fig. l, the left hand side of the drawing isvin general related to the section of the apparatus which supplies oxygen to the face mask and belly bladder 11, while the right hand side is related to the section of the apparatus which supplies oxygen to the restraining tubes orcapstaus of the partial pressure suit. Both sections are supplied with oxygen at the assumed 70 p.s.i.g. and also at the assumed 3.4 p.s.i.a., the latter from, the control pressure regulator 23 through the branch lines leading from this regulator as hereinafter described.

The mask section of the apparatus includes a mask diaphragm valverindicated generally kat .4,0 and which is apagar? shown as having a hollow casing 41 which, as best shown in Fig. 3, can be in common with the casing 41a of the diaphragm valve for the suit section of the apparatus. The common casing 41, 41a for the diaphragm valves 40 and 130 have a common medium pressure oxygen chamber 42 supplied with oxygen directly from the line 15 at the assumed 70 p.s.i.g. The casing 41 includes a circular rim 43 to which is tted a circular cap or cover 44 and a flexible diaphragm 45 has its rim clamped orcompressively sealed in the rim 43 by the cap or cover 44 so as to form two chambers 46 and 48- on opposite sides of the diaphragm 45. The diaphragm is urged toward the chamber 46 by a light spiral compression safety pressure spring 49 interposed between the cap or cover 44 and the central part of the diaphragm 45 which diaphragm carries, preferably on its side facing the chamber 46, a relatively large metal disk 50.

The chamber 48 is a control pressure chamber maintainedv at the assumed minimum pressure of 3.4 p.s.i.a. by thev control pressurerregulator 23 through the lines 51 and 52'leading from the chamber 25 in the control pressure regulator 23 to the control pressure Ychamber 48 of the mask diaphragm valve 40 as bestshown in Fig. l. The chamber 46 is a demand chamber in communication with the mask 10 as hereinafter described so that the pressure iiuctuations caused by the inhalation and exhalation of the pilot moves the diaphragm 45 back and forth.

This movement of the diaphragm 45 serves to admit oxygen from the medium pressure oxygen supply chamber 42 to the mask 10 for inhalation by the pilot, this admission of medium pressure oxygen being under control of a demand valve indicated generally at 57.

For this purpose the casing 41 is provided with a cylindrical recess or bore 54 which opens into the demand chamber 46 and has its axis directed toward the center of the diaphragm 45 and the metal disk 50 carried thereby. The bottom of the cylindrical bore or recess 54 forms an annular seat or shoulder 55 facing the diaphragm 45 and surroundingl a passage or bore 56 leading to the medium pressure oxygen supply chamber 42.

A metal washer vSti seats against the shoulder 55 and on this washer is seated a rubber disk 59 provided with a coaxial opening which registers with a small opening provided in a lower. stationary valve disk 60. This lower stationary valve disk 60 has a raised rim 61 which supports an upper stationary valve disk 62 in such manner as to provide a chamber 63 between the stationary valve disks'60 and 62. This chamber 63 has anv opening 64 registering with a passage 65 communicating with a line 66 which supplies oxygen to the mask 10 and belly blad der 11 Vas hereinafter described'.

The upper stationary valve disk 62 is provided with a downwardly directed teat 68 having a through opening through which a stem 69 fixed to a valve head 70 extends, this valve headbeing cup-shaped with its rim bearing against the underside of the rubber disk 59 around the central opening through this rubber disk. A retaining rim 71 having a large central opening 72 holds the stationary valve disks 60' and 62 in the bore 54.

A cup-shaped rubber seal 73 has its rim clamped between 'the retaining ring 71 and the upper stationary valve disk 62. This rubber seal 73 is made in the form of a rubber membrane and has its cup-shaped part projecting into the demand chamber 46, this cup-shaped part having al conical center which extends toward the valve head 70 and is provided with a central sleeve 74 which tightly embraces the valve stem 69. lt will be seen that this cup-shaped seal 73 positively prevents the escape of medium pressure oxygen from the medium pressure supply` oxygen chamber 42 into the demand chamber 46 to cause turbulence or iluctuation of pressures in the demand chamber.

The free end ofthe stem 69 can terminate in a knob 7S, whichl is arranged to engage the plate 50 on the diaphrasmt, Y

fl`he-;oxygeu supply line66 `to the mask -10- terminates in the nozzle 76 of a mask injector 78. This injector. nozzle 76 is surrounded by the shell or casing 79 of the injector 78 and which casing can be made of two parts 80 and 81 connected by screws 82, as best shown in Fig. 4, with the nozzle 76 as a separate part with its enlarged rim 83 clamped between these two casing parts as shown. Behind the injector nozzle 76 a sensing line 84 establishes communication between the interior of the injector casing 79 and the demand chamber 46. The nozzle 76 dischargesinto a neck 85 of the injector casing 79 and thence into a line 86 leading to the` mask 10. A branch line S8 leads to the belly bladder 11.

After being initially influenced -by the inhalation of the pilot, the sensing line 84 comes largely under the inuence of the injector 78 so that the mask diaphragm valve 40 is partially self-energizing with a part of the required suction supplied by the injector 78. To prevent overcontrol by the injector 78 and to place the diaphragm valve 40 at all times under control of the breathing of the pilot, means are provided for adjustably diminishing the effect of the injector 78 on the sensing line 84, these means being preferably constructed as follows: `The numeral 90 represents a control valve, the effect of which is adjusted by the adjustment of a control screw 91. This valve 90 is in a bypass line having one end 92 connected to the line 66 supplying oxygen to the nozzle 76 of the mask injector 78 and having its other end 93 connected to the demand chamber 46. As best shown in Fig. 5, the casing for this valve is made of two complementary castings 95 and 96 which are secured together by screws 9S and jointly form a chamber 99, one face ofwhich is provided with the ports for the lines 92 and 93. The screw 91 is provided with a head 100 opposite these ports so that when the screw is turned, this head 100'is moved to block olf these ports to a greater or less degree and thereby control the rate of flow of oxygen from theend 92 of the bypass to its end 93. A set screw 101 can be used to hold the adjusting screw 91 in any set position.

In addition to maintaining the required mask and belly bladder pressures at high altitudes, it is also important that the apparatus be capable of getting rid of excess mask and belly bladder pressure when the plane loses altitude or under sudden decompression. To this end the apparatus forming the subject of the invention regulates the mask and belly bladder pressure when conditions call for a progressive reduction as well as when conditions call for a progressive increase in the pressure of the oxygen supply. To relieve or reduce excess mask and belly bladder pressure Whenconditions require such reduction, the mask pressure relief valve indicated generally at 195 is provided, this relief valve being con# structed as follows:

This relief valve is made of two counterpart sections 108 -and 169 joined together by screws 110 and with the rim of a flexible diaphragm 111 clamped between the rims of the two casing sections 198 and 109. This diaphragm forms two chambers 112 and 113, the chamber 112 containing a light spiral compression spring 114 which urges the diaphragm 111 toward the chamber 113. The diaphragm carries a metal disk 107. The relief valve is referenced to the constant minimum pressure, such as the assumed 3.4 p.s.i.a., maintained by the control pressure regulator 23. To this end a branch line 115 from the outlet lines 51 and 52 of the control pressure regulator 23 communicates with the chamber 112. The other chamber 113 communicates through a line 1'16 with the demand chamber 46 of the diaphragm valve mechanism 40, this line preferably having a lter 11S. The flow of oxygen from the demand chamber is under control of a check valve head 119 which, as best shown in Fig. 6, normally seats against a rubber disk or seat 120 surrounding the orifice 121 in the casing 109 and through which oxygen is supplied from the line 116.- The chamber 113 in which this check valve head 119 *is located is vented; as indicated at 122, to the cockpit and it will be seen that when the cockpit or ambient pressure is above 3.4 p.s.i.a and when the pressure in the demand chamber 46 of the diaphragm valve mechanism 40 exceeds cockpit or ambient pressure, the check Valve head 119 is lifted and the excess pressure Yof the oxygen in the demand chamber `46 is relieved through the vent 122. When, however, the cockpit pressure falls below 3.4 p.s.i.a., the outlet pressure from the control pressure regulator 23 through the lines 51, 52 and 115 urges the diaphragm 111 to hold the check valve head 119 closed and thereby permit the build-up of the required oxygen pressure in the demand chamber 46 of the diaphragm valve mechanism 40.

Referring to the right hand side of Fig. 1 which is particularly related to the section of the apparatus which supplies oxygen to the restraining tubes or capstans 12 of the partial pressure suit at a higher than mask pressure when high altitudes are reached, this higher capstan pressure being a minimum of 3.4 p.s.i.a. plus at least four times the differential between this minimum and the ambient or cockpit pressure, as previously described.

The suit pressure section of the apparatus includes a diaphragm valve mechanism having a casing or housing l41a which, as previously indicated, is preferably in common with the housing or casing 41 for the diaphragm valve mechanism `46 of the mask section of the apparatus. The casing or housing 41a is shown as being of cylindrical form and as having an internal chamber 131 which is a suit pressure chamber. The casing or housing-41a is open-ended and the rim of a diaphragm 132 is sealed against the rim of the housing or casing by aflat ring 134 and a collar 135 which is secured to the rim of the casing or housing 41a in any suitable manner. The diaphragm 132 carries a central metal disk or plate 136 which is arranged on the suit pressure chamber side of the apparatus. The rim of a second diaphragm 138 is clamped against the outer rim of the collar by a cap or cover 139. The chamber 140 between the diaphragms 132 and 138 is maintained at ambient or cockpit pressure and for this purpose is provided with a vent 141. The chamber 142 between the diaphragm 138 and the cap or cover l139 is a minimum pressurechamber. This minimum pressure is maintained by the control pressure regulator 23 and for this purpose a line 143 provides communication between the chamber 25 of the control pressure regulator 23 and the minimum pressure chamber 142 of the diaphragm valve mechanism 130. Accordingly, the assumed minimum 3.4 p.s.i.a. is maintained in the minimum pressure chamber 142. The diaphragm 138 carries a large metal disk 145.

`Oxygen under the assumed medium pressure of 70 p.s.i.g. is supplied under control of a demand valve indicated generally at 57a to the suit pressure chamber 131. The medium pressure oxygen is supplied to this demand valve from the medium pressure oxygen chamber 42 which, as previously described, also supplies oxygen to the demand valve 57 for the mask pressure section of the apparatus. The demand valve 57a is identical with the demand valve 57 which serves the mask pressure section of the apparatus and hence the same reference numerals have been used and distinguished by the sulx a and the description of this demand valve 57a is not repeated. The rounding end 75a of its stem 69a is arranged in close proximity to the center of the metal disk 136 secured to the diaphragm 132.

This demand valve 57a controls the supply of oxygen from the medium pressure oxygen chamber 42 to a line 66a leading to a suit injector 78a. This suit injector is identical with the mask inject0r'78 serving the 'mask section of the apparatus and the same reference numerals have been applied with the parts of the suit injector 78a distinguished by the suffix a. As with the mask injector 78, the line 66a terminates in -a nozzle 76a which disy` genas?? charges into an injector casing 79a toward an outlet line 86a Which terminates in the restraining capstans or tubes 12 of the partial pressure suit. Behind the injector nozzle 76a, a sensing line 84a establishes communication between the interior of the injector casing 79a and the suit pressure chamber 131.

The numeral 150 represents a motion transmitting device or relay from the diaphragm 13d to the diaphragm 132, this relay operating (when the larger diaphragm is moved toward the diaphragm 132 by the minimum pressure, assumed to be 3.4 p.s.i.a., in the chamber 142 preponderating over the ambient or cockpit pressure in the chamber 14%) to first engage and then move the diaphragm 132 to the left thereby to move the stem 69a of the demand valve to the left so as to cock its valve head 70:10uY the rubber facing 59a and permit the flow of 70 p.s.i.g. oxygen from the line 15 and medium pressure oxygen chamber 42 through the bore 56a past the cocked valve head 70a and through the chamber 63a, opening 64a and passage 65a to the line 66a leading to the suit injector 78a and thence to the restraining capstans or tubes 12 of the partial pressure suit. This motion transmitting device or relay 150 is shown as comprising a stem 151 formed integrally with the disk 145 carried by the diaphragm 13S and projecting toward the center of the diaphragm 132. This stem 151 has an adjustable head ,15,2 adapted to engage-that face of the diaphragm 132 which cncloses the ambient or cockpit pressure chamber 140. The adjustable head 152 is part of a screw for a threaded shank 153 screwing into the stem 151 and a lock washer 154 is provided for maintaining the adjusted setting of the head 152. The effective area of the disk l145 is preferably live to six times the effective area of the disk 136.

As with the mask pressure section of the apparatus, in addition to maintaining the required suit pressures at high altitudes, it is also important that the apparatus be capable of unloading excess suit pressure when the plane loses altitude or under sudden decompression. To relieve or reduce excess suit pressure in the restraining capstans or tubes 12, when conditions require such reduction, a'control compensated relief valve indicated generally at 105a is provided. This control compensated relief valve, as shown in Fig. 7, is similar in construction to the controly compensated relief valve 105 (Fig. 6) serving the mask section of the apparatus and the same reference numerals have been employed and distinguished by the suix a. An important distinction between the control compensated relief valves 165 and 105a is that the check valve head 119 of the valve 105 is proportionately larger than the check valve head 1194i of the control valve 1ll5a, the purpose of this differential in size of these check valve heads being to maintainthe required .differential between suit pressure and mask pressure when the apparatus is under control of the relief or unloading valves 105, 10541 as when the airplane is descending toward the assumed 35,000 feet altitude.

The check valve head 119a'controls the discharge of oxygen from the suit pressure chamber 131 through a line 116e and filter 118a into the relief chamber 113a which is vented at 122a. The relief valve 105e is related to the minimum pressure maintained by the control pressure regulator 23 through the lines 51` and 52 which maintain this pressure, assumed to be 3.4 p.s.i.a., in the chamber 112:1 of the relief valve. As with the relief valve `105, the chainbers 112a and 113:1 are separated by a diaphragm Illa and which is urged toward the check valve head 119:1 by a light spring 1140 which serves to maintain a slight positive pressure in the suit pressure .section of the apparatus at all times by biasing the check valve head 119i: toward its closed position.

Operation 8 complete' his mission in the event of loss of cockpit pren sure or to enable him to survive hailing out at high altitudes. To this end, even with a pressurized cockpit, the apparataus supplies the aviator with oxygen at a pressure slightly in excess of cockpit pressure so that his blood will be substantially free from nitrogen in the event of sudden loss of cockpit pressure at high altitudes.

For such preoxygenation, oxygen is supplied to the mask 10 of the aviator in response to his inspiration demand. Thus oxygen, under the assumed pressure of 70 p.s.i.g. from the ship supply 19 or emergency bottle 20, through the line 15, medium pressure oxygen chamber 42 to the passage 56, presses against the cup-shaped valve head 70 and holds its rim lirmly against the rubber disk 59. Accordingly, the stem or rod 69 of this demand valve is held in a position perpendicular to this valve seat disk 59. In this position the rounded end of this valve rod or stem is held in closely spaced relation to the center of the metal plate 50 on the side of the diaphragm 45 enclosing the demand chamber 46.

When the user of the mask 10 inhales, the pressure in theV mask is reduced and through the supply tube 86, injector housing 79 and sensing line 84 the pressure in the demand chamber 46 is reduced. Since ambient or cockpit air pressure (via the lines 52 and 51, chamber 25 of 'the control pressure regulator 23 and open vent passage 36) is `impressed on the side of the diaphragm 45 forming the control air pressure chamber 48, this reduction in pressure in the demand chamber 46 moves the diaphragm 45 toward fthe chamber 46 and causes its plate 5l) to contact and tip the stem 69 of the demand valve 57 laterally. This tips the cup-shaped valve head 70 laterally and hence separates one side of the rim of the valve head from the rubber disk 59 and permits the moderate pressure oxygen from the supply chambers 42 and 56 to escape through the valve chamber 63 and passages 64 and 65 to the oxygen supply line 66 for the mask. From this line the oxygen ows through the casing 79 of fthe injector 7S and thence through the line 86 to the mask 10 to satisfy the inhalation of the aviator.

Such medium pressure air as may enter through the end opening of the nipple 68 of the upper stationary valve disk 62 is prevented from escaping into the demand chamber 46 because of the cup-shaped iiexible valve seal 73 Iwhich has its inner part snugly fitted around the valve stemY 69 and its outer part snugly clamped against the upper face of the upper stationary valve disk 62 by the retaining ring 71. It such medium pressure air were permitted to escape directly from the demand valve 57 to the demand chamber 46, the control of the pressure in this demand chamber from the mask 10 would be in part lost and also such escaping medium pressure oxygen would set up undesirable eddy currents in the demand chamber 46 which would adversely influence the operation of the diaphragm 45. While the cup-shaped flexible l seal 73 effectively isolates the demand chamber 46 from the medium pressure oxygen controlled by the demand valve 57, this seal leaves the valve stem 69 free to move in response to the movement of the diaphragm 45.

-ln flowing through the mask injector 78, the main stream of oxygen ows through the nozzle 76 thereby to provide an aspirating effect or pressure reduction in the injector housing 79. This reduces the pressure in the sensing tube 84 and in the demand chamber 46 so as to tend to hold the diaphragm 45 to the left as viewed in Flig. 3 and the valve head 70 open. Accordingly the injector 78 tends to make the demand valve 57 partially selbenergizing when once opened, so that little effort is required byV the user of the mask 19 in continuing. his inhalation, thereby to reduce chest fatigue. v

The eect of the injector 78 is adjustably reduced by'. thev regulating valve in the bypass line 92, 93. It will .be seen that this line 92, 93 is across the lines 66 and 84 to the injector and that hence by opening this bypass line 92, 93` to a greater degree the injector 78 is rendered progressively less etfective in reducing the pressureV in the sensing line 84 and demand chamber 46 and hence in rendering the demand valve 57 self-energizing as above described.

After the inhalation -is complete, the pressure in the mask and belly bladder 11, as Well as in the sensing line 84 and demand chamber 46, rises through the admission of moderate pressure oxygen past the demand valve 57, as above described, to the valve of the ambient or cockpit pressure exerted against the side of the diaphragm 45 forming the ambient or control pressure chamber 48. When this counter-pressure in this chamber 48 is exceeded by the rising pressure of oxygen in the demand chamber 46, the diaphragm moves to the right as viewed in Fig. 3. This moves the metal plate 50 out of contact with the free end 75 of the valve stem 69 and permits the demand valve parts to assume the closed position shown. In this position the valve head 70 is held firmly closed by the static pressure of the oxygen supply until the user again inhales to repeat the cycle just described. At the altitude at which the aneroid 30 becomes operative, and at all higher altitudes, this aneroid maintains a constant pressure in the chamber 25 and hence, through the lines 51 and 52 in the control pressure chamvber 48.l It Will be assumed that this constant minimum pressure is 3.4 p.s.i.a., this being close to the lowest limit which can be safely applied to the body. This constant minimum pressure is determined by the internal pressure in the enclosed or sealed aneroid 30 and the setting of the drilled vent screw 35.

Thus oxygen is supplied at the assumed 70 p.s.i.g. pressure through the restricted oriiice 22 which is proporf tioned to admit, say, 2O cubic centimeters per minute to the chamber 25. When this pressure being built up in the chamber 25 exceeds the internal pressure of the aneroid 30 it contracts this aneroid axially until its end 33'moves away from the adjusting vent tube 35. When this occurs the oxygen escapes through the bore 36 of the screws 35 until the pressure in the chamber 25 falls to such value as to permit the internal pressure in the aneroid 30 to expand this aneroid axially and engage the end of the screw 35 to again seal the escape passage or vent 36 to the cockpit of the airplane. The constant minimum pressure so maintained in the chamber 25, through the lines 51 and 52, is maintained in the control pressure chamber 48 and is impressed against the corresponding side of the diaphragm 45.

'pressure regulator 23, through the lines 51 and 52, in the control pressure chamber. Accordingly, the inhalation etort required by the aviator never exceeds that required to pull the diaphragm 45 against the minimum pressure of 3.4 p.s.i.a. maintained in the control pressure chamber 45, vregardless of how low the ambient pressure drops as the airplane rises above 35,000 feet.

. Referring now to the suit section of the apparatus,

'when the airplane rises above about 35,000 feet and the stant minimum pressure of 3.4 p.s.i.a. in its chamber 25, thediaphragm 138 is positioned toward the diaphragm i132 sincethe constant minimum pressure of 3.4 p.s.i.a.

control pressure regulator '23 operates to maintain a conis maintained in the chamber 142 (through line 143),

.while the ambient pressure (vent 141) in the chamber `140 on the other side of this diaphragm 138 is now below this. value of 3.4 p.s.i.a. With the continued movement {ef the diaphragm 13s toward the diaphragm 132, the relay plates 145, 152 connected by the stem 151, is moved to- -'or motion transmitting device 150, comprising the end motion transmitting-device 150 continues` until the metai plate 136 on the diaphragm 138 engages and moves the free end of the stem 69a of the demand valve 57a. This tips the cup-shaped valve head 70a laterally and hence separates one side of the rim of this valve head from the rubber facing 59a and permits the moderate pressure oxygen at the assumed 70 p.s.i.g. pressure to escape from the supply chambers 42 and 56a through the valve cham'- ber 63a and passages 64a and 65a into the oxygen pres'- sure supply line 66a. Through the injector 78a this builds up the pressure in the suit capstans 12 or tubes .which contract the partial pressure suit about the limbs of the aviator and this increased pressure is also reflected back through the sensing tube 84a into the suit pressure chamber 131.

When the suit pressure in the chamber 131 rises, through such admission of moderate pressure oxygen past the demand valve 57a, to a suflicient value, the diaphragm 132 is moved by this rising pressure in the chamber 131 toward the chambers 140 and 142 until it releases the free end a of the stem 69a of the demand valve 57a and permits this demand valve to close and cut off the further admission of moderate pressure oxygen to the suit pressure chamber 131 as well, of course, as the capstans o'r tubes 12 of the partial pressure suit.

The suit injector 78a functions to render the demand valve `57a self-energizing to a degree in the same manner as the mask injector 78 functions to render the demand valve 57 partially self-energizing. Thus, as oxygen supplied by the opened demand valve 57a discharges from the nozzle 76a, it creates a suction in the injector housing 79a and sensing tube 84a. This tends to reduce the pressure in the suit pressure chamber 131 as long as .inthe direction to tip the valve stem 69a and thereby hold the demand valve head 70 open.

The demand valve 57a closes when the suit pressure in the chamber 131 builds up to a predetermined differential between the minimum pressure of 3.4 p.s.i.a. maintained in the constant pressure chamber 142 and the ambient pressure maintained in the ambient pressure chamber 140. This diterential is determined by the relative effective sizes of the diaphragms 138 and 132, as measured by the effective areas of their plates 145 and 136 respectively. The relative size of these plates is such that, say, the suit pressure in the suit pressure chamber 131 equals live times the difference between the minimum pres'- sure of 3,4 p.s.i.a. maintained in the chamber 142 and the ambient pressure maintained in the ambient pressure cham- .ber 140. Since the demand valve 57a can only be eifective after the ambient pressure in 140 drops below 3.4 p.s.i.a., this formula is only effected when ambient pressure' is below the constant pressure maintained in chamber 142.

It will be seen that this equation of suit pressure (chamber 131) being equal to live times the difference between the minimum pressure (chamber 142) and the ambient pressure (chamber 140) is derived from the fact that the constant pressure (chamber 142) is impressed on the full area of the diaphragm plate 145 which is assumed to have an effective unit area of five, whereas the ambient pressure (chamber 140) is impressed on the opposite side of this diaphragm plate 145 andthe suit pressure (chamber 131) is impressed against the diaphragm plate 136 assumed to have an effective unit area of one.

Before the air plane reaches an altitude of 35,000 feet and hence is subjected to an ambient pressure greater than 3.4 p.s.i.a., the demand valve 57 is opened and closed only in response to the respiratory demand of the user as rst above described. When, however, this altitude is "exceeded, assuming the cockpit to have lost its pressurizaftion, the constant 3.4 p.s.i.a. pressure maintained in chamber 48 preponderates over the ambient pressure 1f maintained in chamber 46 to move `the diaphragm 45 to the left and to tip theopen demand-valve. 1

`It will be seen that as the unpressurized airplane rises above 35,000 feet, the demand Valve 57 maintains a minimum mask pressure in the mask and belly bladder 11 of 3.4 p.s.i.a. due to this minimum constant pressure being maintained by the control pressure regulator 23 -in the control pressure chamber 48. It will also be seen that at this time a pressure corresponding to five times `the differential between this minimum pressure of 3.4 p.s.i.a. and ambient pressure is maintained in the tubes or capstans 12 of the partial pressure suit due to the relative sizes of the plates 145 and 136 of the diaphragme 138 and 132, respectively, forming the constant pressure chamber 142 and the ambient pressure chamber 140.

While this part of the apparatus will maintain these conditions as the unpressurized airplane rises above 35,000 feet, provision must also be made to proportionately unload .or adjust these pressures downwardly as the airplane descends toward the 35,000 feet altitude. Considering rst the mask section of the apparatus, the minimum pres sure of 3.4 p.s.i.a. is maintained in the chamber 112 of the relief valve 105 and ambient pressure is maintained in the chamber 113 through the vent 122. The valve 119 is acted upon by the diaphragm 111 which is moved in response to the differential between the ambient pressure in the chamber 113 and the constant pressure of 3.4 .p.s.i.a. maintained in chamber 112 when the airplane is vabout 35,000 feet. This valve head 119 is also acted upon by the pressure.exerted against it by the pressure maintained in the demand chamber 46. As the unpres- .surized airplane descends from altitudes higher than 35,000 feet, the ambient pressure in chamber 113 increases 4thereby to relieve the pressure of the diaphragm 111 against the valve head 119 and to permit lthis valve head to open and permit escape of oxygen from the demand chamber 46 until the pressure of the oxygen in this demand chamber 46 against the bottom of the valve head 119 is brought into balance with the differential between the minimum constant pressure of 3.4 p.s.i.a. maintained in the chamber 112 and the ambient pressure maintained -in the chamber 113.A This gradual unloading of the mask pressure in the demand chamber 46 continues until the airplane descends -below 35,000 feet when the aneroid 30 v remains withdrawn from the vent screw 35 so that both `the chambers 112 and 113 of the relief valve 105 are .subject to ambient pressure so that the valve head 119 is` held closed only by the light action of the spring 114. This spring serves to maintain a slight positive pressure -of the oxygen in the demand chamber 46 so that if an -ascent should be again made above 35,000 feet, the aviator will be preoxygenated so that in the event of any pressure failure there will not be an `excess of nitrogen in his blood. j

It is equally important, of course, to similarly unload ox'. reduce the suit pressure in the capstans or tubes 12 of the partial pressure suit and in the suit pressure chamber 1'31 as the airplane descends toward the critical altitude of about 35,000 feet. This unloading or reduction is eifected by the relief valve 105e, the chamber 112:1 of which, at altitudes above 35,000 feet, is maintained at 3.4 p.s.i.a. The chamber 113a on the other side vof the `diaphragm 111:1 of this relief valve 105a is at yambient ypressure and an important feature is that the effective area ofk plate 107:1 carried by the diahpragm 111:1 is ve timesthe effective area of the valve head 119:1. As the airplane descends toward an altitude of 35,000 feet, the ambient pressure in chamber 113a rises thereby to reduce l,the eifect of the diaphragm 1 11a in holding closed the valve head 119e. Accordingly, the suit pressure impressed on vthe opposite side of the valve head 119:1 will open this valve and escape through the vent 122:1 as the airplane reaches progressively lower altitudes in descending toward 35,000 feet. Due, however, to the differential in size between the diaphragm plate 107:1 and the valve head 119:1', such escape is only permitted at a rate to stillmaintain the suit pressure in the tubes or capstans 12 at the assumed pressure of ve times the difierential between ambient pressure in chamber 113:1 and the constant minimum pressure maintained in chamber 112:1.

When the unpressurized airplane descends below 35,000 feet the aneroid 30 withdraws from the Vent screw 35 to render the chamber 112:1 open to the atmosphere so that both sides of the diaphragm 111:1 are subjected 'to atmospheric pressure and the valve head 119a is only held closed by the relatively light spring 114i: which serves to maintain a slight positive pressure in the suit capstans or tubes -12 so that any leakage will be outwardly and so that such leakage can be detected by the flow of oxygen when no oxygen is required.

From the foregoing, it will be seen lthat the present invention provides a simple and effective differential pressure'gas supplying apparatus which accomplishes the various objectives set forth. It will also be seen that the invention Ycan be widely varied as to its details of construction and the invention is therefore not to be construed as limited to the particular embodiment shown and described but is to be accorded the full range of the equivalentsl comprehended by the accompanying claims.

Iclaim: j

1. A diiferential pressure apparatus for supplying oxygen to the mask of an aviator, comprising a hollow casing, an internal movable wall across the interior of said casing and dividing said casing into two chambers, means arranged tomaintain a predetermined minimum pressure in one of said chambers, an oxygen conduit arranged externally of said chambers to supply pressurized oxygen directly to said mask, demand valve means in said oxygen conduit, means responsive to the movement of Ysaid movable wall toward and from said other of said chambers and opening and closing said valve means, and a sensing conduit connecting said other of the chambers with said 4mask end of said oxygen conduit.

2. A differential pressure apparatus as set forth in claim 1 wherein said means arranged to maintain a predetermined minimum pressure in said one of said chambers includes va control pressure regulator including a casing having a vent opening, a restricted conduit connecting the interior of said regulator casing with said pressurized oxygen', a conduit connecting the interior of said regulator casing with said one of said chambers, and an internally pressurized bellows mounted in said regulator casing and having a free end expansible toward and contractable from said vent opening to close and open Said vent opening in response to the internal pressure in said regulator casing.

, 3. A `differential pressure apparatus as set forth in claim 1 wherein said oxygen conduit includes an injector nozzle, an injector casing surrounding said injector nozzle and in which injector casing the discharge from said nozzle 'has an aspirating effect, and a conduit generally in line with said nozzle and connecting said injector casj ingwith said mask, and wherein said sensing conduit comprises a relatively small sensing tube connected at one end to said injector casing and at its other end to said other of said chambers and operating to vary the pressure in said other of said chambers in response to the inlhalation demands of the aviator.

4. A differential pressure apparatus as set `forth in claim 3 wherein a bypass conduit connects said other of said chambers with .said oxygen conduit in advance of said injector nozzle to reduce the aspirating eftect of said .injector nozzle.

5. A differential pressure apparatus as set forth in `claim 4 wherein a regulating valve is arranged in said bypass conduit. Y

6. A differential pressure apparatus as set forth in claim l additionally including a relief valve comprising a hollow casing, an internal movable wall across the im terior of said relief valve casing and dividing said relief valve casing into two chambers one of which is vented to the atmosphere and the other of which is connected with said means to maintain a predetermined minimum pressure, a conduit providing communication between said vented chamber and said mask to permit the discharge of pressurized oxygen from said mask, a vent valve controlling the tiow of oxygen from said last conduit to said vented chamber, and means responsive to the movement of said movable wall in said relief valve casing and arranged to open and close said vent valve.

7. A dilerential pressure apparatus as set forth in claim 6 wherein a light spring is arranged in said relief valve casing and biases the movable wall therein in the direction to close said vent valve.

8. A differential pressure apparatus for supplying gas under pressure to the suit of an aviator, comprising a hollow casing, at least two internal movable walls across the interior of said casing and dividing said casing into at least three chambers, means arranged to maintain a mini-.num pressure in one of said chambers, means arranged to maintain ambient pressure in another of said chambers, a gas conduit arranged to admit gas under pressure to said suit, a valve in said gas conduit, means arranged to open and close said valve in response to the joint movement of said movable walls, an injector nozzle in said gas conduit, an injector casing surrounding said injector nozzle and in which injector casing the discharge from said nozzle has an aspirating etfect, and a relatively small sensing tube connected at one end to said injector casing and at its other end to the third of said chambers to render said valve partially self-energizing in response to the discharge of gas from said nozzle.

9. A differential pressure apparatus for supplying gas under pressure to the suit of an aviator, comprising a hollow casing, at least two internal movable walls across the interior of said casing and dividing said casing into at least three chambers, means arranged to maintain a minimum pressure in one of said chambers, means arranged to maintain ambient pressure in another of said chambers, a gas conduit arranged to admit gas under pressure to said suit, a valve in said gas conduit, means arranged to open and close said valve in response to the joint movement of said movable walls, a sensing conduit providing communication between the third of said chambers and said suit, and a relief valve comprising a hollow casing, an internal movable wall across the interior of said relief valve casing and dividing said relief valve casing into two chambers one of which is vented to the atmosphere and the other of which is connected with said means to maintain a minimum pressure, a conduit providing communication between said vented chamber and said third chamber to permit the discharge of pressurized gas from said suit, a vent valve controlling the flow of oxygen from said last conduit to said vented chamber, and means responsive to the movement of said movable wall in said relief valve casing and arranged to open and close said vent valve.

10. A differential pressure apparatus as set forth in claim 9 wherein a light spring in said relief valve casing biases the movable wall therein in the direction to close said vent valve.

References Cited in the le of this patent UNITED STATES PATENTS 2,703,572 Seeler Mar. 8, 1955 2,755,799 Marty July 24, 1956 2,867,227 Meidenbauer Jan. 6, 1959 

